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Temperature-dependent phase transition in [001]-oriented 0.72Pb(MgNb)O-0.28PbTiO single crystals
摘要： Temperature-dependent dielectricity and polarization of [001]C-oriented 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 relaxor-based ferroelectric single crystals were studied by using a combined method of the X-ray di?raction, dielectric spectrum, polarization-electric (P-E) ?eld hysteresis loops, and the Landau-phenomenological theory. Results show that the room-temperature rhombohedral phase experiences a rhombohedral-monoclinic-tetragonal coexisting state, then transforms to tetragonal phase, and ?nally to cubic phase during the zero-?eld-heating process. The six-order Landau-type thermal expansion parameters for the tetragonal phase were determined by using the typical characteristics at the cubic-tetragonal phase transition in the temperature range from 91 °C to 113 °C. The calculated dielectric curve, polarizations, and P-E loops ?t well with the experimental results. The phase stability and piezoelectricity are further studied and compared with those of the PMN-0.36PT single crystal. The provided methods and obtained Landau parameters can be used for further studies on the relaxor-based ferroelectric single crystals.
关键词： PMN-PT single crystals,Phase transition,Double hysteresis loops,Landau expansion parameters
更新于2025-11-14 17:28:48
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Effective synthesis of nanoscale anatase TiO <sub/>2</sub> single crystals using activated carbon template to enhance the photodegradation of crystal violet
摘要： Nanoscale anatase TiO2 single crystals were successfully synthesized using three kinds of activated carbon (AC) templates through a simple sol–gel method. The optimal photocatalyst (T‐WOAC) was obtained using wood‐based AC template. X‐ray diffraction, transmission electron microscopy and Brunauer–Emmett–Teller analyses revealed that T‐WOAC possessed a small crystallite size of 8.7 nm and a clear mesoporous structure. The photocatalytic properties of samples were then evaluated through photodegradation of crystal violet (CV). Results implied that the photocatalysts prepared using the AC templates exhibited superior photocatalytic activity to that of the original TiO2. This enhancement may be due to the small crystallite size, large specific surface area and pore volume of the catalysts prepared with ACs. T‐WOAC showed high photocatalytic activity, CV degradation of 99.01% after 120 min of irradiation and k = 0.03914 min?1, which is 3.9 times higher than that of the original TiO2 (k = 0.00994 min?1). This result can be mainly attributed to the application of WOAC with moderate specific surface area and pore volume to produce T‐WOAC. Alkaline conditions benefitted the photodegradation of CV over photocatalysts. This work proposes a possible degradation mechanism of CV and indicates that the fabricated photocatalysts can be used to effectively remove CV from aqueous solutions.
关键词： photocatalyst,anatase TiO2 single crystals,sol–gel,crystal violet,activated carbon
更新于2025-11-14 17:04:02
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single crystals
摘要： 3at.%Tm3+:Ca1?xGdxF2+x (x = 0, 0.005, 0.01, 0.02) single crystals were grown by the vertical Bridgman method, where Gd3+ ions play the role of manipulating ions for local structure to form a disordered lattice site. Spectral properties of these crystals were investigated. Compared to 3at.%Tm3+:CaF2, the spectral parameters of 3at.%Tm3+:Ca1?xGdxF2+x were drastically enhanced in a large scale. LD pumped lasers have been demonstrated in the crystals for the first time. For CW operation, the slope efficiency up to 49.7% was achieved with output power of 1.927 W at 1970 nm. With a birefringent quartz plate, wavelength-tunable laser operation with a tuning range of more than 176 nm was realized.
关键词： Spectral properties,Single crystals,Gd3+ ions,LD pumped lasers
更新于2025-09-23 15:23:52
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Synthesis and Electrical Transport Properties of CuInGaTe2
摘要： Copper Indium Gallium di-telluride (CIGT) single crystals were synthesized by a special modified Bridgman technique for crystal growth. Our XRD patterns clearly exhibited single phase. The temperature dependence of the electrical conductivity σ(T), Hall coefficient RH(T) in CuInGaTe2 single crystals have been demonstrated over the temperature range 143-558 K for the first time. The Hall coefficient sign confirms the samples displays the p-type conducting. The temperature dependence of the conductivity, Hall coefficient, Hall mobility, and charge carriers concentration were investigated were presented with a clear and effective pictures. CuInGaTe2 single crystals revealed electrical band gaps (or "transport gaps") ranging from 0.64 eV to 0.85 eV. The results obtained from electrical conductivity and carrier concentration revealed the sample p-type with acceptor energy level equal to ≈ 0.027 eV. From the obtained experimental data, the main fundamental physical constants and others for crystals under consideration have been estimated.
关键词： Single crystals,Electrical conductivity,Cu–III–VI2 Chalcopyrite semiconductors
更新于2025-09-23 15:22:29
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Additional phase transition in a PbZr <sub/>0.87</sub> Ti <sub/>0.13</sub> O <sub/>3</sub> single crystal
摘要： PbZr1-xTixO3 (PZT) ceramics are one of the most known and widely used piezoelectric materials. In order to understand the origin of the high piezoelectricity it is essential to also understand its phase diagram. Many recent papers reported on the modification of PZT phase diagram based on ceramic experimental data. This is due to difficulties to get good quality single crystal samples. We have succeeded in getting a good quality single crystal with x= 0.13. Based on temperature changes of elastic properties we confirmed the existence of additional phase transition appearing in the PbZr0.87Ti0.13O3. The temperature dependence of the elastic properties was investigated by means of piezoelectric measurements and Brillouin light scattering. We discussed the correlation between anomalies of the elastic properties found in these measurements, and suggested that, except for the two well-known phase transitions, these anomalies point to another phase transition below Tc. The structure and symmetry of this crystal have been tested with use of the x-ray diffraction at the room temperature.
关键词： x-ray diffraction,phase transitions,elastic properties,piezoelectricity,PZT single crystals
更新于2025-09-23 15:22:29
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The effect of machining on domain configuration in [001]-oriented tetragonal Pb(Mg <sub/>1/3</sub> Nb <sub/>2/3</sub> )O <sub/>3</sub> –PbTiO <sub/>3</sub> single crystals
摘要： Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals have attracted increasing attention in electro-optic and nonlinear optical applications. In this paper, it was found that the domain configuration of PMN–PT single crystals was influenced by machining and electric process, such as cutting, grinding, polishing, and electrical field poling. The ordered herringbone/stripe domain pattern can be changed into an unexpected disordered domain state in tetragonal PMN–PT crystals which was observed in some crystal samples. Those chaotic structures can decrease transmittance and increase possibility of cracking during poling. However, the disordered domain pattern can be eliminated by a temperature cycling process. Crack-free single-domain crystals were successfully obtained by electric field poling, exhibiting complete optical extinction in an orthogonal polarized light microscope. The results suggest that the domain configuration of PMN–PT single crystals is sensitive to machining process and can be controlled by proper temperature and electric field.
关键词： domain configuration,optical properties,electric field poling,PMN–PT single crystals,temperature cycling,machining
更新于2025-09-23 15:21:21
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Effect of Uncontrollable Impurities on the Absorption Spectrum of a NaGd(WO4)2 Laser Crystal
摘要： Three NaGd(WO4)2 single crystals were grown by the Czochralski method using charges of different chemical purity. The impurity compositions of the grown crystals were analyzed by inductively coupled plasma mass spectrometry. The optical absorption spectra of the crystals were measured, and the effect of uncontrollable impurities on their optical properties and color was analyzed. The green color encountered in NaGd(WO4)2 crystals in some cases was shown to be due to the uncontrollable impurities of d elements, among which the chromium impurity had the most significant effect.
关键词： optical absorption,impurity purity,color centers,single crystals,zinc tungstate,ytterbium
更新于2025-09-23 15:21:01
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Nucleation-controlled growth of superior lead-free perovskite Cs3Bi2I9 single-crystals for high-performance X-ray detection
摘要： The organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. However, the issues raised by the toxic lead element and marginal stability due to the volatile organic components have severely limited their potential applications. In this work, we develop a nucleation-controlled solution method to grow large size high-quality Cs3Bi2I9 perovskite single crystals (PSCs). Using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. We ?nd that X-ray detectors based on PSCs exhibit high sensitivity of 1652.3 μC Gyair?1 cm?2 and very low detectable dose rate of 130 nGyair s?1, both desired in medical diagnostics. In addition, its outstanding thermal stability inspires us to develop a high temperature X-ray detector with stable response at up to 100 °C. Furthermore, PSCs exhibit high X-ray imaging capability thanks to its negligible signal drifting and extremely high stability.
关键词： nucleation-controlled growth,high sensitivity,X-ray detection,lead-free,perovskite single crystals
更新于2025-09-23 15:21:01
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Preparation and optical properties of Ho3+-doped YSZ single crystals
摘要： Single crystals of yttria-stabilized zirconia (YSZ) doped with different contents of holmium were prepared by the optical floating zone method, and their structures and phase composition were characterized by XRD and Raman spectroscopy. These showed that the metastable tetragonal phase was stabilized by the substitutions. Transmittance of each of the Ho3+-doped YSZ single crystals was larger than 85% in the visible region. Measurements of fluorescence spectra indicated a strong emission at a wavelength of 553.5 nm, and two weak emission peaks at 671 nm and 759 nm when the crystals were excited by light with a wavelength of 448 nm. The YSZ doped with 0.75 mol% of Ho2O3 had a relatively higher fluorescence intensity and possessed high color purity (99.7%) in the green region, indicating that it can be used to produce efficient green emission.
关键词： fluorescence,single crystals,Ho3+,YSZ,optical properties
更新于2025-09-23 15:21:01
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Crystal growth and optical properties of Ca <sub/>3</sub> TaGa <sub/>3</sub> Si <sub/>2</sub> O <sub/>14</sub> single crystals
摘要： Transparent yellowish Ca3TaGa3Si2O14 single crystals were grown in Ar+(0.5–3)% O2 along the Y-axis by the Czochralski technique. The structural perfection of Ca3TaGa3Si2O14 samples was studied by X-ray topography and rocking curve methods. Topograms and rocking curves along the surfaces of the Y- and Z-cuts were studied before and after surface treatments (polishing and etching). Transmittance spectra were measured in the wavelength range of 200–3300 nm. Optical anisotropy was studied along the X- and Z-axes, and dichroism along the X-axis. The dispersions of the refractive index No and speci?c rotation of the polarization plane were determined using spectrophotometric methods.
关键词： optical properties,Czochralski technique,single crystals,Ca3TaGa3Si2O14,X-ray topography
更新于2025-09-23 15:21:01